The present invention is related to an optical arithmetic comparator, and more specifically, to an optical comparator and method for comparing multiple digits simultaneously and displaying their common value.
A common task that arises in computing is to show that two or more numbers are equal. A comparison operation of only two numbers can be accomplished by showing that their difference is zero. When more than two numbers are to be compared, however, the method usually utilized is to compare the numbers in pairs and then show that all the pairs are equal via a logical tree.
The above described comparison of more than two numbers takes more than one process step to complete, even in parallel logic, thereby delaying the comparison operation. In addition, the comparison operation is further delayed in conventional electronic computing systems in which the speed is inherently limited by the RC time constants of the interconnecting wiring.
Recent progress in the field of optical computing has led to the demand for optical components, such as optical comparators, capable of overcoming the inherent speed limitations of conventional electronic computing systems. For example, U.S. Pat. No. 4,604,707 issued to Yamashita et al discloses an optical comparator that compares two binary input light patterns. The light patterns are scanned serially by an acoustic wave device in order to effect a bit-by-bit comparison of the input patterns. While providing some advantages over conventional electronic comparators, the speed of the disclosed optical comparator is limited to the speed limitations of the acoustic wave device and still requires multiple comparisons of bit pairs.